In the photopolymer field where ultraviolet light is used to expose a photopolymer composition, it has been common to illuminate the workroom in yellow light for work to proceed under relatively high visibility. Work under yellow light with photopolymer films has been equivalent to work under red lights with silver halide films, except that higher roomlight visibility is standard for photopolymer films.
It had long been recognized that undesirable reactions take place with photopolymer compositions which require corrective measures. Thommes U.S. Pat. No. 3,144,331 teaches a preexposure step employing at least 70% of the intensity of actinic radiation required to expose a photopolymer film as a means of restoring or photoconditioning a photopolymer film to its full potential for photopolymerization. Rust et al. U.S. Pat. No. 3,598,584 discloses a presensitizing step for a photopolymer film with actinic radiation of relatively low intensity as compared to that employed in the imaging step.
Peter P. Klemchuk, Influence of Pigments on the Light Stability of Polymers; A Critical Review, Polymer Photochemistry 3 (1983) 1-27 deals with interactions which occur in pigment polymer mixtures. Among the possible mechanisms discussed to explain some of the complex interactions are singlet and triplet state transitions. In particular light absorbing dyes are capable of energy transfers whereby singlet oxygen was produced.
In spite of all that was known concerning the effect of dyes and the deficiencies of photopolymer films, there has been no recognition that a beneficial effect could be obtained by correctly regulating preparation and exposure of a photopolymer film with a combination of a specific class of dyes in the photopolymer composition and use of actinic radiation of a wavelength normally employed to prevent undesirable reactions.